Device for detecting attempts at fraud on an apparatus for reading and writing on a chip card

ABSTRACT

A device for detecting attempts at fraud by connection of an electric feed line (13) to an apparatus for reading and writing on a chip card (3) essentially comprises a resonance unit (6) coupled to a contacting element (2) of the apparatus, and a measuring device (7). In the resonance unit (6) a generator (4) which is coupled to a resonator (1) by way of an impedance converter (5) generates a standing wave. The feed line (13) disturbs the properties of the resonator (1), that being detected by the measuring device (7) and evaluated.

BACKGROUND OF THE INVENTION

This is a continuation-in-part of application Ser. No. 07/967,620, filedOct. 28, 1992, now abandoned.

The invention relates to a device and a method for detecting attempts atfraud on an apparatus for reading and writing on a chip card, forexample a smart card.

Such devices are advantageously used in service systems--for example inautomatic-payment phone units (payphones)--which operate with electronicchip cards.

In an attempted fraud situation, use is made of an altered chip card ora card which is externally similar thereto, with connecting pointsarranged in the same way, at least one of the connecting points beingconnected to an electrical feed line of a unit which is present outsidethe writing and reading apparatus and which is used to carry out theattempted fraud. The attempt at fraud can be detected by checkingwhether there is an inadmissible feed line of that kind.

A device is known (EP 0 468 848 A1) in which a signal in a feed line, ifsuch is present, of a card receiver, can be detected by means of aninductive sensor and selected filter which is connected on the outputside thereof, use being made of the fact that in the reading and writingoperations a chip card is processed by signals at a known standardizedfrequency.

A transmitter in the card receiver at one end of the chip card and areceiver at the other end thereof, and to use a feed line, if such ispresent, as a transmission medium, coupling occurring galvanically atthe transmission end while at the receiving end coupling is effectedinductively (EP 0323 347 A1, FR 2 554 262, FR 2 646 260) or capacitively(FR 2 646 260), or coupling occurring at the transmission endinductively and at the receiving end inductively (EP 0 447 686) orgalvanically (EP 0 454 570) is also known.

Also known is a device having an oscillator (FR 2 646 261) which has afrequency-determining element which is moved over the chip card so thatthe feed line, if present, causes a disturbance at the output of theoscillator.

In the known devices, mechanical devices such as for example antennae ormovable sensors are to be arranged in the card receiver in the region ofthe chip card in such a way that they are substantially protected fromdamage.

The invention is based on the problem of providing a reliable andwell-protected device for certainly detecting attempts at fraud on anapparatus for reading and writing on a chip card.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided an attempted fraud detection device which has a resonance unitwith a resonator which is coupled to the connecting point and whoseelectrical properties can be varied by the feed line and detected by themeasuring device.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in greater detail hereinafterwith reference to the drawings in which:

FIG. 1 shows the principle of a device for detecting attempts at fraudon an apparatus for reading and writing on a chip card,

FIG. 2 shows an alternative configuration of the device with a conductoras a resonator,

FIG. 3 shows an alternative configuration of the device with a parallelresonant circuit as a resonator,

FIG. 4 shows an alternative configuration of the device with a seriesresonant circuit as a resonator,

FIG. 5a shows a plan view of an alternative configuration of the device,and

FIG. 5b shows a side view of parts of the device shown in FIG. 5a,

FIG. 6 shows an alternative configuration of the device with a conductoras a resonator, with at least two tappings,

FIG. 7 shows a comprehensive diagram of an alternative configuration ofthe device with a resonator according to FIG. 6, and

FIG. 8 shows an embodiment of a resonator according to FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 reference numeral 1 denotes a resonator which is galvanicallycoupled to a contacting element 2 of a known apparatus (chip cardreader/writer) for reading and writing in the memory on an also knownchip card 3 and which together with a generator 4 and an impedanceconverter 5 forms a resonance unit 6, the output of the generator 4being connected to the resonator 1 by way of the impedance converter 5.A measuring device 7 with an alarm output 8 for an alarm signal has atleast one input connected to the resonance unit 6, and an output whichis fed back to the resonance unit 6 by way of a control member 9.

Besides the contacting element 2, the apparatus for reading and writingon the memory of the chip card 3 has further similar contacting elementswhich however are not shown, a processing unit 10, and a card receiver(not shown in the drawing) with an entry opening for the chip card 3.Each of the contacting elements is connected to the processing unit 10by way of an electric line 11.

The chip card 3 is a value card which has at least one electroniccomponent, for example a microcomputer or a memory, which can beaccessed by way of a number of connecting points 12 for the writing andreading apparatus, which has a contacting element 2 for each of theconnecting points 12. The number of the connecting points 12 and thearrangement thereof on the chip card 3 is standardized, in which respectthere are different standards.

As is known, an altered chip card 3 or a card which is externallysimilar thereto, having connecting points 12 arranged in the same way,is preferably used for an attempt at fraud. At least one of theconnecting points 12 is connected to an electric feed line 13 of a unit14 which is disposed outside the apparatus. When the chip card ispresented to the apparatus, any feed line 13, if present, is connectedto the corresponding contacting element 2. The unit 14 used for theattempted fraud is for example a measuring unit or a simulator.

A device for detecting the attempt at fraud by connection of the feedline 13 to the contacting element 2 comprises the resonance unit 6, themeasuring device 7, the control member 9 and a screening means 15 whichis disposed between the resonance unit 6 and the lines 11; details ofthe device and the mode of operation thereof are described hereinafter.

The generator 4 whose output impedance is tuned by the impedanceconverter 5 to the resonator 1 generates in the resonator 1 anelectromagnetic oscillation at a frequency of for example one GHz.

Preferably the resonance unit 6 is so tuned that a standing wave isproduced in the resonator 1 at least when the feed line 13 to theconnecting point 12 connected to the resonator 1 by way of theconnecting element 2 is missing. The feed line 13 causes the propertiesof the resonator to be disturbed so that its input impedance and theoscillation are measurably altered.

Advantageously, the resonator, as shown in FIG. 2, is an electricalconductor or a waveguide which is in the form of a wire, a stranded wirelead, a conductor track or a hollow body and which has at least onetapping A galvanically connected to the input of the measuring device 7.The tapping A is preferably disposed in the vicinity of a node of thestanding wave.

In a first alternative configuration of the device, the measuring device7 measures the electrical voltage at the tapping A and compares themeasurement value to a predetermined reference value in respect of thevoltage which occurs at the tapping A when the feed line 13 is notconnected to the contacting element 2. An attempt at fraud is recognizedby virtue of the magnitude of the difference between the measurementvalue and the reference value, and the alarm signal is generated forexample at the output of a threshold switch which belongs to themeasuring device 7.

Advantageously, the measuring device 7 has processing means such as forexample amplifiers or filters so that the measurement value can bereliably detected.

The alarm signal is advantageously evaluated in known manner by theprocessing unit 10.

The control member 9 permits a feedback of the measurement value to thegenerator 4 and/or the impedance converter 5 so that if necessary thefrequency of the generator 4 and the impedance at the output side of theimpedance converter 5 can be varied from the measuring device 7.

The screening means 15 on the one hand protects the processing unit 10from disturbances which are caused by the resonance unit 6 while on theother hand it protects the device from troublesome influences of thelines 11.

In a second alternative configuration, advantageously, the voltage orthe impedance at the input of the resonator 1 is measured and comparedto a predetermined reference value in respect of the impedance orvoltage. The reference value is the impedance of the resonator 1 or thevoltage at the resonator 1 without the feed line 13 at the contactingelement 2.

The first and second alternative configurations can be successfullycombined.

In a third alternative configuration of the device, the frequency of theoscillation in the resonator 1 is altered by a variation at thegenerator 4 until the voltage at the tapping A reaches a given targetvalue. The target value is equal to that value of the voltage which,with a predetermined reference value in respect of the frequency of theoscillation, occurs at the tapping A, if the feed line 13 is notconnected to the contacting element 2. The measuring device 7 ascertainsa measurement value of the frequency of the oscillation, for example byway of a further input connected to the output of the generator, andcompares the measurement value to the frequency reference value. Anattempted fraud is recognized on the basis of the magnitude of thedifference between the measurement value and the reference value.

The third and second alternative configurations can be successfullycombined.

In a fourth alternative configuration of the device, the resonator 1 iseither a parallel resonant circuit comprising a coil L_(p) and acapacitor C_(p), as shown in FIG. 3, or a series resonant circuitcomprising a coil L_(S) and a capacitor C_(S), as shown in FIG. 4, thequality of which is altered by the feed line 13. Advantageously, in thisalternative configuration the voltage or the impedance at the input E ofthe resonator 1 is measured and compared to a predetermined referencevalue in respect of the impedance or voltage, which the resonator 1 haswithout the feed line 13 at the contacting element 2.

By virtue of the fact that the electrical properties of the resonanceunit 6 which is galvanically connected to the contacting element 2 andwhich operates in the Gigahertz range are measurably influenced by afeed line 13 in the present device, a feed line 13 can be certainlydetected, irrespective of its diameter, its position or its screening.

The device can be arranged entirely outside the card receiver as it isonly coupled to the contacting element 2. No precautions are required inthe space between the electronic component (microcomputer or memory) ofthe chip card 3 and the entrance opening of the card receiver.

The resonator 1 is preferably coupled to that contacting element 2 whichcontacts the potential reference point (signal ground) of the chip card3.

In FIG. 5, instead of the galvanic connection to the contacting element2 (FIG. 1), the resonator 1 has a coupling member 16 for a non-galvaniccoupling of the resonator 1 to the connecting points 12 and thus to thefeed line 13. Coupling occurs capacitively or inductively depending onthe respective nature of the coupling member 16.

For capacitive coupling of the resonator 1, the coupling member 16 is sodesigned that a voltage at the output of the resonator 1 is influencedby way of an electrical field by the feed line 13.

The coupling member 16 for capacitive coupling advantageously has alayer 17 of a metal, which is parallel to the two largest flat faces ofthe chip card 3 and which is arranged opposite a zone enclosing theconnecting points 12 of the chip card 3, and which approximately coversthe surface of the zone.

For inductive coupling of the resonator 1, the coupling member 16 is soarranged that a current in the resonator 1 is influenced by way of amagnetic field by the feed line 13.

The electric feed line 13 which is coupled to the resonator 1 by way ofthe coupling member 16, at one of the connecting points 12, alters theproperties of the resonator 1, which are detected by the measuringdevice 7.

With the further configuration of the device, it is possible to detectthe attempted fraud without the connecting points 12 of the chip card 3being galvanically connected to the contacting elements 2. The attemptedfraud can therefor advantageously be detected prior to the applicationof the contacting elements 2 to the connecting points 3 or even uponinsertion of the chip card 3 into the apparatus for reading and writingon the chip card, the properties of the resonator 1 being advantageouslysubstantially independent of the contact elements 2 and the lines 11.

In addition the properties of the resonator 1 are substantiallyindependent of the installed electronic component on the chip card 3;the device can therefore be advantageously used in an unchanged form fordifferent configurations of the chip card 3.

FIG. 6 shows part of a fifth alternative configuration of the device inwhich the resonator 1 is an electric conductor or a wave guide, wherebythe resonator 1 is equipped with the tapping A connected to the input ofthe measuring device 7 and with the coupling member 16. The resonator 1has a second tapping B which is connected to another input 18 of themeasuring device 7. The second tapping B is preferably located inproximity of a node of the standing wave. The electric voltage attapping A can also be measured at tapping B by means of the measuringdevice, as described earlier.

FIG. 7 shows the resonator 1 connected to the coupling member 16 withinput E and with the two tappings A and B, with generator 4, impedanceconverter 5, measuring device 7 and control member 9. The measuringdevice 7 is advantageously equipped with a first input member 19connected to the tapping A on the input side, with a second input member20 connected to the tapping B on the input side, with a first thresholdswitch 21 and with a second threshold switch 22, whereby the twothreshold switches 21 and 22 are connected to the control member 9 onthe output side.

The generator 4 is preferably equipped with a phase control circuit(PLL) 23, with a voltage-controlled oscillator (VCO) 2 connected on theoutput side to the impedance converter 5 and with a low-pass filter 25in circuit between the phase control circuit 23 and the oscillator 24,whereby a frequency input 26 of the phase control circuit 23 isconnected to the input E of resonator 1 following the output of theimpedance converter 5 and whereby a multi-pole control input 27 of thephase control circuit 23 is connected via bus 28 to the control member9.

The phase control circuit 23 can be substantially in the form of abuilding block of type MC145191.

A reference input 29 of the first threshold switch 21 is connected to areference input 30 of the second threshold switch 22 and is connectedvia a compensation member 31 at the input E of the resonator 1. Thevoltage changes at input E of resonator 1 caused by fluctuations in theenvironmental temperature can be compensated for in such manner by thecompensation member 31 that a reference signal at the output of thecompensation member 31 or at the two reference inputs 20 and 30 is to agreat extent independent of temperature.

The first threshold switch 21 is provided with a signal input 32 whichis connected to the output of the first input member 19. A signal input33 of the second threshold switch 22 is connected to the output of thesecond input member 20.

The resonator 1, made in the form of an electric conductor or of a waveguide is equipped with several conductor elements coupled by couplingmembers if necessary, whereby at least one of the conductor elements isinstalled so as to be capable of displacement if this should benecessary, for instance if this is required by the construction or thefunctioning of the device used to read and write in the memory of thechip card 3.

Reference number 34 in FIG. 8 designates a first conductor element and35 a second conductor elements of the resonator 1 made in the form of awave guide at one end of which input E is provided and the other end ofwhich is connected to the coupling member 16. The form of the firstconductor element 34 can be adapted to the construction and theavailable space in the device to read and write in the memory of thechip card. The first conductor element 34 is equipped with the twotappings A and B and with a first coupling member 36. One end of thesecond conductor element 35 ends with the coupling element 16 and theother with a second coupling member 37.

The first conductor element 34 is preferably a flexible cable and aprinted circuit contains the coupling member 16 and the second conductorelement 35 with coupling member 37.

The first coupling member 36 is located in a plane e₁ of which one partis delimited by an imaginary border 38 which also encloses the firstcoupling member 36.

The second coupling member is located in a second plane e₂ which ispreferably parallel with the first plane e₁ and one part of which isdelimited by another imaginary border 39 which also contains the secondcoupling member 37. The two imaginary borders 38 and 39 enclosecongruent surfaces.

The second conductor element 35 can be displaced in the direction of anarrow 40 at least so far that the two conductor elements 34 and 35 canbe coupled optimally by the two coupling members 36 and 37 in theresonator 1. An advantageous coupling of the two conductor elements 34and 35 is achieved if the two borders 38 and 39 in FIG. 8 coincide.

The device to detect attempted fraud can be connected to the chip card 3through a movement of the second conductor element 35 in direction ofarrow 40 while a movement in the direction opposite to arrow 40disconnects it from the chip card.

If necessary the movements in direction of arrow 40 are initiated byinserting the card 3 into the chip card 3 memory read/write device.

In an advantageous embodiment of the resonator 1 the two input members19 and 20 are located directly on the corresponding tapping A or B andcan be made in form of SMD's (surface mounted devices), for example.

If necessary the tappings A or B are provided on resonator 1 directlynext to each other or are physically made in the form of one tapping towhich the measuring device 7 can be connected.

An advantageous embodiment of the coupling elements 36 and 37 can beachieved by one single winding on the first conductor segment 34 or onthe second conductor segment 35 for each.

At least two different values of the frequency of the generator 4 can beset by the control member 9, whereby a first value may be equal to 500MHz and a second value 455 MHz for instance.

The length of the second conductor segment 35 is advantageously adaptedto one quarter of the wavelength in resonator 1 at the first value ofthe frequency while the length of the first conductor segment 34 isadvantageously a multiple of this half wavelength.

The description of a process in which attempted fraud can be detected bymeans of the device according to FIG. 7 follows.

In a first step the frequency of the generator 4 is set to a firstvalue. The voltage at tapping A is detected by the first input number 19and is compared in the first threshold switch 21 with the referencesignal appearing at the reference input 29. If the detected voltage isnot within an expected first range the attempted fraud is recognized,the process is stopped and the chip card 1 is refused.

If the voltage detected at tapping A is within the expected range thefrequency of the generator 4 is set to the second value in a secondstep. The voltage at the second tapping B is detected by the secondinput member 20 and is compared in the second threshold switch 22 withthe reference signal appearing at the reference input 30. If thedetected voltage is not within an expected second range the attemptedfraud is detected and the chip card 1 is refused.

The chip card 1 is accepted only if the voltage detected at tapping Alies within a first range during an oscillation with a first value ofthe frequency and if the voltage detected at the second tapping B lieswithin a second range during an oscillation with a second value of thefrequency.

Due to the fact that one voltage is detected at the resonator 1 andcompared with a desired value for each of at least two different valuesof the frequency the attempted fraud can also be detected if theeffective length of feeder 13 is a multiple of half the wavelength ofthe oscillation at one of at least two values of the frequency.

The device according to FIG. 7 has a first node without feeder 13(FIG. 1) at the first value of the frequency at tapping A and a secondnode at the second value of the frequency at tapping B.

An advantageous method to determine the optimal first value of thefrequency of the oscillation in resonator 1 comprises changing thefrequency in a certain direction by means of the control member 9 andthen detecting a first threshold frequency f₁ when an output signal atthe first threshold switch 21 changes from a first extreme value (e.g.,a maximum) into a second extreme value occurring within the frequencyrange of the fist node (e.g., a minimum). The frequency is alteredcontinuously in the same direction and a second threshold frequency f₂is detected when the output signal changes back from the second extremevalue to the first extreme value.

The optimal first value of the frequency is a mean value of the twothreshold frequencies f₁ and f₂ ; the first value is advantageously thegeometric center (f₁ *f₂)^(1/2) of the two threshold frequencies f₁ andf₂.

The optimal second value of the frequency is found by applying theabove-described method to a second node whereby an output signal at thesecond threshold switch 22 is used.

It is advantageously possible to carry out a method to determine the twooptimal values of the frequency of the oscillation in resonator 1automatically. As required, each embodiment of the device isindividually equalized according to the method.

I claim:
 1. A method of detecting attempts at fraud by connection of anelectric feed line (13) to a connecting point (12) of a chip card (3) inan apparatus for reading and writing in a memory on the chip card (3),having a measuring device (7) connected to a resonance unit (6) having aresonator (1) coupled to the connecting point (12) and whose electricalproperties are varied by the feed line (13) and detected by themeasuring device (7), comprising measuring the impedance at the input ofthe resonator (1) and comparing said impedance to a reference value,said reference value being related to the impedance of the resonator (1)without the feed line (13) being connected to said connecting point(12).
 2. A method of detecting attempts at fraud by connection of anelectric feed line (13) to a connecting point (12) of a chip card (3) inan apparatus for reading and writing in a memory on the chip card (3),having a measuring device (7) connected to a resonance unit (6) with aresonator (1) which is coupled to the connecting point (12) and whoseelectrical properties are varied by said feed line (13) and detected bythe measuring device (7), comprising generating an oscillation resonator(1), measuring voltage at the resonator (1) and comparing said measuredvoltage with a desired value which is set at the resonator (1) when thefeed line (13) is not connected to the connecting point (13).
 3. Amethod of detecting attempts at fraud by connection of an electric feedline (13) to a connecting point (12) of a chip card (3) in an apparatusfor reading and writing in a memory on the chip card (3) , having ameasuring device (7) connected to a resonance unit (6) with a resonator(1) which is coupled to the connecting point (12) and whose electricalproperties are varied by said feed line (13) and detected by themeasuring device (7), comprising generating an oscillation with afrequency having a first value in the resonator (1), measuring thevoltage at the resonator (1), comparing said measured voltage with adesired value, wherein said desired value is measured at the resonator(1) when the feed line (13) is not connected at the connecting point(12), adjusting said frequency to a second value different from saidfirst value, measuring said voltage again, comparing said again measuredvoltage with another desired value wherein said another desired value ismeasured at the resonator (1) when the feed line is not connected at theconnecting point (12), and accepting said chip card (3) only if theagain measured voltage at the resonator lies within a predeterminedrange based on the first and second values of the frequency.
 4. A methodof detecting attempts at fraud by connection of an electric feed line(13) to a connecting point (12) of a chip card (3) in an apparatus forreading and writing in a memory on the chip card (3), having a measuringdevice (7) connected to a resonator (1) in a resonance unit (6) at atapping (A), wherein said resonator (1) is coupled to the connectingpoint (12) and has electrical properties which are varied by said feedline (13) and detected by the measuring device (7), comprising measuringthe voltage at said tapping (A), and comparing said measured voltagewith a desired value of the voltage appearing at said tapping (A) whenthe feed line (13) is not connected to the connecting point (12).
 5. Amethod of detecting attempts at fraud by connection of an electric feedline (13) to a connecting point (12) of a chip card (3) in an apparatusfor reading and writing in a memory on the chip card (3), having ameasuring device (7) connected to a resonator (1) in a resonance unit(6) at a tapping (A), wherein said resonator (1) is coupled to theconnecting point (12) and has electrical properties which are varied bysaid feed line (13) and detected by the measuring device (7), comprisingmeasuring the impedance at the input of the resonator (1), comparingsaid measured impedance to an impedance reference value, wherein saidimpedance reference value is related to the impedance of the resonator(1) when the feed line (13) is not connected to the connecting point(12), measuring the voltage at the tapping (A), and comparing themeasured voltage to a voltage reference value, wherein said voltagereference value is related to the voltage which occurs at the tapping(A) when the feed line (13) is not connected to the connecting point(12).
 6. A method of detecting attempts at fraud by connection of anelectric feed line (13) to a connecting point (12) of a chip card (3) inan apparatus for reading and writing in a memory on the chip card (3),having a measuring device (7) connected to a resonator (1) in aresonance unit (6) at a tapping (A), wherein said resonator (1) iscoupled to the connecting point (12) and has electrical properties whichare varied by said feed line (13) and detected by the measuring device(7), comprising varying the frequency of an input signal at theresonator (1) until the voltage at said tapping (A) reaches a giventarget value, whereupon the frequency of the input signal is measuredand compared to a predetermined reference value related to the frequencymeasured when the feed line (13) is not connected to the connectingpoint 12, wherein the voltage at the tapping (A) is at the given targetvalue when the resonator (1) oscillates at the predetermined referencevalue.